braking problem today - any tips???

tod914 · 06-26-2003, 04:09 PM

Was a super hot day today. Well over 90. Drove my car down to a shop to check on somethings - about 35 minute drive. Everything was fine. On the way back, aside from the minor starting clitch, my brakes seemed like when i stepped on them, the car would just slowly come to a stop. Peddle was a little spongy but didnt sink much more than it normaly does. I just had new ss lines and 19mm master put in. New super blue fluid too about 2 months ago. Got the car home, pumped the peddles for a bit and then it seemed to brake ok again. Is it likey its just air in the lines? Funny how it took 2 months to start a problem. Reservoir is full and no leaks at the calipers. Any advice appreciated.
The other thing is, I had the car up on jack stands, wheels off. I noticed with the front rotors, there would be a very slight rubbing with the pads when i turned it by hand. I planned on doing the rotors bearings and pads soon. Would that indicate a sticky caliper? Do the calipers need a rebuild? they dont leak. Maybe just air in lines?? Today was real hot so I dont know if there is any correlation to the problem.

SGB · SGB's Garage

I haven't done the brakes on my car in a while but I seem to remember that the front pads "float", just occaisionally brushing the rotor, while the rears have a clearance screw to adjust for a slight gap 'tween the two. I remember wondering why the front calipers didn't incorporate the adjustment screw. So.... I think yer brakes 'r OK. I would guess that the work you did freed up a bubble or somethin'. Try bleeding the brakes if it still doesn't seem right. Sometimes my brake peddle get softer after a while. I don't know how the air gets in there. I always figured it was their as little "micro-bubbles" that eventually coalesce into a single blob that compresses more easily.

Jim Smolka · 06-26-2003, 06:05 PM

Could be the MC starting to fail. With the heat, the metal expands etc.

tod914 · 06:30 PM

Jim the master cyl is brand new - Ill see if i can bleed the lines. give me a base point anyway

SGB - I see your from huntsville. I was stationed there for 2years in the Army - very laided back duty station - I actually was working for civilians. 83-85

Thanks for the tips guys. I'll try bleeding first. Hopefully thats all it is. Would the hot weather make that problem more evedent?

mikester · 06-26-2003, 07:38 PM

With heat metal is not the only thing that expands.

If there is any air in your system it will expand as well causing even more of a mushy feeling.

efeinsmith · 06-27-2003, 08:58 AM

One other item in the 914 brake system (and one often overlooked) is the proportioning valve, located at the bottom of the firewall (behind the seats). It governs how much brake pressure goes to the rear brakes, but can be a place that air gets trapped in.

Eric

Bleyseng · Bleyseng's Garage

Bleeding the system is a pain, trying to get all the air out especially from the prop. valve. I have found that installing Speed Bleeders is the ticket to a hard petal. Everything must be in excellent condition and the venting clearance set, Then flush using one can of SuperBlue and the Speed Bleeders. Man, what a difference it makes.
I do this once a year before I AX the car

Geoff

John Rogers · 06-27-2003, 11:05 AM

If you replaced the m/c I'd try to measure the free play that the manual calls for in the pedal. It is very easy to have a new m/c that is slightly different in tolerances than the old one and the clearance will dissapear. This will prevent the m/c from fully retracting and will make proper bleeding nearly impossible. I'd also recommend that the prop valve be replaced with a tee and then there will be no problems with air in the rear portion of the brake system. I agree with the speed bleeders too. Good luck.